If you'll notice, the design of the piston leaves a LOT to be desired. The round dish is a detriment to good squish/quench action, and in this case it's made even worse by a rather large 45 degree chamfer around the outer edge of the piston deck. That leaves a scant 1/2" band of the top of the piston to provide the quench effect, and that's just not enough.
A much better choice if a dished piston is needed is a reverse dome or D-cup type piston (this one is for a SBC 383 stroker):
X3 on the camshaft- much too much duration @ 0.050" lift. It would run better all the way around w/a cam in the 222-228 duration @ 0.050" range. Nothing wrong w/using a split pattern cam w/the Vortec head, though.